Today, civil aeroplanes determine their vertical descent profile with the help of navigation databases, data entered into the active flight plan and performance data for the aeroplane. The vertical profile is established by the Flight Management System FMS which computes the trajectory associated with the performance of the aircraft allowing best compliance with the operational constraints.
The predicted vertical descent and approach profile, considers certain assumptions about the instants of extension of the actuators influencing the deceleration of the aircraft, namely the slats, the flaps, the landing gear and the airbrakes, these instants also being termed subsequently the instants of setup of aerodynamic configurations.
Today, these instants of setup of aerodynamic configurations are defined by speeds provided directly by a performance database. The speeds conventionally used are the maneuvering speeds, that is to say the minimum speeds of setup of configuration in automatic management mode. These instants therefore do not vary except for the airbrakes which depend on the performance of the aeroplane and slopes predicted. This means that these instants take account neither of the actual meteorological conditions, nor of the procedure. These instants are nevertheless essential for the computation of the deceleration profile, of the flight time, of the fuel consumption and of the noise level perceived on the ground.
For example, the slats and flaps are extended at the maneuvering speeds, otherwise called F/S/O respectively for the aerodynamic configuration termed FULL (or 3) in which the slats and flaps are extended to a high degree, termed landing, the aerodynamic configuration termed 2 in which the slats and the flaps are extended to a lesser degree, and the configuration termed 1. These speeds are the minimum speeds Vmin at which the aerodynamic configurations can be extended when the aeroplane is in automatic management mode by the flight management system FMS. Moreover, the maximum speeds of setup of configuration Vmax are called the VFEs and ensure that the loads on the wings remain acceptable. These latter speeds are provided to the pilots in the cockpit.
Moreover, the vertical slopes of the current procedures are often frozen for simplifying reasons (computation of geometric profile relying on the altitude constraints of the procedure for example).
In the current economic and ecological context, airlines are seeking to reduce the operational costs of flights as well as to reduce their environmental footprint, that is to say to decrease environmental nuisance such as noise or emissions of greenhouse effect gases through reductions in fuel consumption.
To achieve these objectives, new approach procedures (lesser noise—no holding pattern) of CDA (Continuous Descent Approach)/CDO (Continuous Descent Operations) type are proposed. They must at one and the same time afford environmental benefits and ensure better determinism especially as regards the predicted end time of the procedure in respect of problems of flow separation on approach by the air traffic control.
Generally, the so-called CDA/CDO flight procedures consist in flying higher with a neutral energy profile, that is to say with a minimum thrust, without using the airbrakes, and with instants of setup of configuration that are optimized in regard to the energy stabilization and sound nuisance.
Thus the implementation of CDA/CDO procedures leads to constructions of very optimized vertical profiles where the room for manoeuvre to rejoin the vertical plan in case of deviation is reduced.
Taking account of this problematic issue, the instants of extension of the slats and flaps therefore play a major role in computing the descent and approach profiles in the field of so-called CDA/CDO flight procedures.
However, current solutions for which the choice of the configuration change speeds is fixed at a single value, are very conservative in this regard, and do not support the reduction of operational costs as one of the objectives fixed by the said CDA/CDO procedures. In particular, the current solutions lead to higher fuel consumption.
Moreover, fixing configuration change speeds at a single value amounts to fixing the deceleration profile and does not make it possible to adjust it as a function of the speed constraints to be satisfied.
Furthermore, current solutions do not correspond to the operational practices of pilots, thus not allowing reliable and precise prediction of fuel consumption and flight time up to landing.
Generally speaking, no adaptive scheme exists today which makes it possible to adapt the speeds of setup of configuration for each flight, according to the particularities of the procedures, of the meteorological conditions, of the constraints of speeds, time, noise and other parameters, even though patent application FR 3005759 A1 describes a method of automatic determination of an optimized descent and approach profile which makes it possible to modify the instants of setup of configuration so as to circumvent non-flyable slope problems. However, the method described does not make it possible to deal with the optimization of the setups of aerodynamic configurations in a more extensive and more complex set of contexts.
The adjustment of the setups of configurations is a major element in adapting the trajectory of the aeroplane and its speed profile to the various operational constraints. However, today, simplified modelling of the sequence for setup of aerodynamic configurations whose instants are generally based on fixed and minimum speeds, does not make it possible to cover the variability of the operational procedures, termed “Dive and Drive” or “CDA/CDO”, and consequently does not represent the current practices of pilots.
The technical problem is to provide a method of automatic determination of an optimized descent and approach profile for an aircraft making it possible to compute speeds of setup of optimized configurations and correspondingly the instants of change of aerodynamic configurations, by considering the loads on the wings and the structure, the maneuvering speeds, the procedure (constraints of speeds, time, noise, slope) and the operational costs (fuel consumption, noise).
The technical problem is to provide a method of automatic determination of an optimized descent and approach profile for an aircraft which allows the pilot to have the choice of an advanced or late deceleration according to customary practices while guaranteeing a sufficient deceleration capacity for the stabilization of the aircraft at 1000 ft AGL (Above Ground Level) under IFR (Instrument Flight Rule) or 500 ft AGL under VFR (Visual Flight Rule).